Radio cabinet and speaker mounting



April 6, 1948. I G. F. DEVINE 2,440,078

RADIO CABINET AND SPEAKER MOUNTING Filed March 17, 1943 Inventor: GeorgeF Devine,

I by .Z -T W l-hs Attorney.

Patented Apr. 20, 1948 RADIO CABINET AND SPEAKER MOUNTING George F.Devine, Easton, Conn., assignor to General Electric Company, acorporation of New York Appli ation March 17, 1943, Serial No. 479,523

3 filairns. 1

My invention relates to cabinets for radio receivers and in particularto the mounting of loud speakers within such cabinets. It is an objectof my invention to-provide a new and improved loud speaker mounting fora radio cabinet to permit the use of larger speakers in such cabinets.

Another object of my invention is to provide an improved radio cabinetin which the speaker is inclined at an angle to the front of thecabinet, thereby permitting the use of a larger speaker in a cabinet ofa given size.

A further object of my invention is to provide an improved speakermounting for a radio cabinet in order to effect certain improvements inthe low frequency sound response thereof.

Still a further object of my invention is to effect certain improvementsin the technique of manufacturing radios by permitting the use ofspeakers of difierent sizes with a single design of chassis.

An important feature of my invention is the mounting of the loud speakerin a radio cabinet at an angle to the front surface of the cabinet,thereby permitting the use of a larger speaker for a given frontalsurface area.

Another feature of my invention is the provision of a speciallydeveloped reflecting surface for use with an inclined speaker in orderto prevent multiple reflections, between the walls enclosing the spacebetween the speaker and the reference to the following description takenin connection with the accompanying drawing, in which Fig. 1 is a frontelevational view, partly broken away, illustrating a radio cabinet ofthe table model type embodying my invention, and Fig. 2 is an enlargedside View, partly in section and, partly broken away, of a portion ofthe cabinet of Fig. 1.

In Fig. 1, I have shown a domestic radio receiver of the familiar tablemodel type, the cabinet thereof having a front surface [El and a topsurface H. The front surface H) has the usual tuning dial I12 disposedthereon, over which moves an index l3 controlled by the usually manuallyoperated knob I4 which also, in the usual manner, controls the tuningadjustment of the conventional unicontrolled tuning condensers or othertuning device. The receiver also includes the-usual volume adjuster l5and a switch l6 for selecting any one of a plurality of radio frequencybands. The knobs I l-l6 are supported by shafts which extend directlyinto the usual radio chassis (not shown) located in the bottom portionof the cabinet.

In order to provide a compact receiver unit, the tuning dial I2 isdisposed directly above the control knobs M-l5 and the loud speaker I7is placed directly above this tuning dial for purposes which areexplained in detail later.

In order to provide a radiocabinet in which both length and height arekept to minimum dimensions, while a large speaker is utliized to providean improved sound output, in the embodiment of my invention shown thespeaker I7 is located above the tuning dial l2 and is inclined at anangle to the front surface It, the angle of inclination being determinedby the frontal surface area available for the mounting of the speakerand the'size-of the speaker which it is desired to use. The geometry ofthe speak er cone determines the limit of the angleof inclination, itbeing undesirable generally to tilt the speaker backwardly so far thatany portion of the cone radiates sound at an angle greater than with theopening in the front of the cabinet. Other factors which enter into theangle of tilt of the speaker are pointed out later.

One manner of mounting the speaker in such a position is best seen inFig. 2 in which the specially shaped speaker supporting member 253 isattached in any suitable manner, such as by gluing, to the top surfacell of the cabinet. The speaker I! has a metal mounting ring 24 which issecured to the member 20 at the upper end of the speaker by screw 25 andat the lower end by means of bolt 2'6 and nut 21. The speaker I! ispreferably of the typeusually used in radio receivers and, supportedbythe ring 24, is the usual cone or diaphragm 28 and field structure 29including a voice coil, not shown, to which are supplied audio frequencyvoltages from the output of the receiver circuit. The-construction ofthe speaker per se forms no part of my invention and the detailsthereof, other than those already pointed out, are not shown.

A decorative cloth or grille 36- of the usual type is provided over thespeaker opening in the front surface ll] of the cabinet. Alternatively,louvers or any other desired type of grille work may be used for thispurpose. A transparent member, such as the glass [8, is provided asmeans to protect the dial l2 and is supported on the front panel of thereceiver by means of clamp l9.

In the conventional type of receiver mounting, the loud speaker usuallyis attached directly to th front panel of the receiver so that theeffective diaphragm diameter of the speaker is limited to the availablefrontal surface area which, in the case of Fig. 2, is indicated by thedimension A. By supporting the speaker at an angle to the front surfaceof the cabinet, however, the effective diaphragm diameter of the speakeris increased to the dimension B. By varyin the angle between the frontsurface H] of the receiver cabinet and the inclined surface 3| of themember 20, the diameter 13 of the speaker may be made considerablygreater than the height A of the frontal space usually available formounting the speaker so that the dimension B may be as much as '75 to100 per cent greater than the dimension A. Such a construction,therefore, permits the use of a larger speaker in a small cabinet andeffects a considerable and desirable improvement in the sound output ofthe receiver.

When the speaker is tilted back in the manner illustrated, some of thesound waves emanating from diaphragm 28 strike against the top oropposite wall of the cabinet and are directed toward the grille 30, theangle of reflection of the sound waves being equal to the angle ofincidence with the opposing surface. As the angle between the surface 3|and the front surface I is increased, ultimately the higher audiofrequencies, When reflected from the opposing surfaces of the cabinet,do not pass directly through grille 30 but instead reflect back upon thecone and upon other surfaces within the cabinet, thus causing multiplereflections of the wave within the cabinet and producing an undesirablesound quality which may be likened to sea shell effect and which iscaused by interference of sound waves within the boundaries of thecabinet.

In order that full advantage may be obtained from my improved speakermounting, the speaker supporting member 2i! is provided with a specialsound reflecting surface 32 in opposition to the cone or diaphragm 28,the purpose of the surface 32 being to direct sound Waves emanating fromthe diaphragm 23 directly to the exterior of the receiver through thecloth or grille 35 without permitting any multiple reflections of thesound waves'within the cavity or enclosure formed by the speaker I1, thesurfaces of supporting member 28, and the grille 30. The special shapeof the sound reflecting surface 32 is developed by tracing the path ofsound waves emanating from the diaphragm 28 to the surface 32 and theexterior of the receiver cabinet, the shape of surface 32 being suchthat these sound waves are reflected within the above-mentioned cavityonly by the surface 32, and are directed by that surface through thegrille 33 to the exterior of the cabinet with substantially no furtherreflection from any of the 7 tion within the above-mentioned cavity. Bytracing in this manner the paths of waves from all points along the cone28 to the inner surface of the member 20 and by adjusting the reflectionangle of these waves from this irmer surface so that all of these wavesare directed through grille 30 without further reflections within thecavity, the shape of the surface 32 required to give the desired resultsis readily obtained.

As stated previously, generally it is undesirable to tilt the speaker I!backwardly with respect to the front panel ID to such an extent that anyportion of the cone diaphragm radiates sound at an angle greater thanwith respect to the opening in front of the cabinet. If this angle ismade greater than 90", it becomes difiicult properly to shape surface32, so that this surface possesses good sound reflecting qualities,without the member 20 itself becoming so large as to consume a portionof the available frontal area. For economy of construction and greatestspace saving, the maximum angle of inclination of speaker I! withrespect to the front panel l0 should be approximately 90 minus the angleindicated at C on the drawing.

The side surfaces 40 of the speaker supporting member 29 may bedeveloped in a manner similar to that explained in connection with thesurface 32 so that substantially all sound emanating from the diaphragm28 is directed through the available frontal opening in the frontsurface Iii without multiple reflections within the cavity orsemi-confined space formed by the member 28 and the speaker I? with thegrille 38. With this construction of the upper surface 32, side wallsurfaces 40 and inclined surfaces 3| of the member 29, the dimensions ofthe above-mentioned cavity or semi-confined space are kept as small aspossible and effect an improvement in the sound output of the speaker I!at the bass end of the audio range which results apparently from abetter loading of the diaphragm 28 by the column of air in thissemi-confined space in front of the speaker. Such a result is commonlyattributed only to a horn type of speaker and not hitherto achieved withthe type of speaker usually employed in the conventional domestic radiore ceiver.

The member 20 may be formed from any suit- I able material, such aswood, or may be molded from a plastic material of the synthetic resintype. With any given radio chassis, by the use of different dimensionsfor the member 20, various sizes of speakers may be used for anavailable amount of frontal surface area in a particular cabinet. Thus,in a cabinet formerly limited to a speaker having a maximum dimension of5 inches, by the use of different sizes of supporting members 20,speakers ranging up to 10 inches in diameter may be employed. Such anarrangement not only effects improvements in the output soundcharacteristics of the receiver, but permits an over-all design of aradio receiver with reduced dimensions for a given speaker size.

Preferably, the dimensions of the sound reflecting'member bothlaterally, i. e. between the side wall portions 49, and rearwardly, i.e. the farthest point of member 20 from grille 3e, are kept as small aspossible in order that the space within the cabinet and behind thespeaker remain as great as possible as well as to form the previouslymentioned cavity to give the effect of a horn type of speaker. In someinstances, where other factors permit, these dimensions may be increasedto obtain the effect of a larger cavity in front of the speaker.Likewise, in order to obtain optimum bass response from theconstruction, the side wall surfaces 49 are fitted tightly to theinclined surface 3|, the upper surface 32, and the top surface I I.

It is thus seen that my invention provides means for improving the audiocharacteristics of a radio receiver by permitting the use of a largerspeaker in a relatively small cabinet. By using a specially shapedreflecting surface developed in the manner disclosed above and forming asemiconfined cavity between the speaker and the front opening in thecabinet, an improved low frequency response is obtained for all sizes ofspeakers.

While I have shown the speaker I! as mounted above the tuning dial andchassis, it is apparent that it may be placed below the chassis withoutincreasing the over-all height of the cabinet. Likewise, the arrangementof my invention may be employed to mount a speaker along one side of acabinet so that a large speaker may be used with only a small amount ofavailable frontal area.

Hence, while I have shown particular embodiments of my invention, itwill of course be understood that I do not wish to be limited theretosince various modifications may be made, and I contemplate by theappended claims to cover any such modifications as fall within the truespirit and scope of my invention.

What I claim as new and desire to secure by I Letters Patent of theUnited States is:

1. In combination, a radio cabinet having an opening therein, acone-shaped sound emitting diaphragm of dimensions substantially largerthan one dimension of said opening and supported within said cabinet atan angle to said opening, a sound wave reflector supported within saidcabinet, said reflector having a pair of angularly related surfaces,said reflector being arranged at such an angle to said diaphragm thatlines perpendicular to the respective sides of said diaphragm andforming equal angles of incidence and reflection with a correspondingone of said surfaces are directed through said opening.

2. A radio cabinet having a front wall having an opening therein, acone-shaped sound emitting diaphragm having a diameter substantiallylarger than one dimension of said opening and supported within saidcabinet at an angle to said wall, a sound reflector within said cabinetarranged at an angle with both said wall and said diaphragm, saiddiaphragm and said reflector having their adjacent edges arrangedsubstantially opposite the middle of said opening and the remote edgessupported respectively adjacent opposite edges of said opening, saidreflector comprising a pair of angularly related surfaces arrangedrespectively to direct sound emitted by opposite sides of said diaphragmthrough said opening.

3. The combination of a cabinet having a wall with an elongated openingtherein, a cone-shaped sound emitting diaphragm having a periphery whosediameter is substantially larger than the small dimension of saidopening being supported within said cabinet, the periphery of saiddiaphragm being located in a plane which intersects the plane of saidopening substantially adjacent one side of said opening, a soundreflector having an edge positioned adjacent the side of said openingopposite to said one side across the small dimension of said opening andincluding a pair of angularly related surfaces, one of said surfaceslying in a plane which intersects the plane of said Iperiphery at theside of said diaphragm opposite said opening and the junction of saidsurfaces being located substantially opposite the middle of saiddiaphragm, the angular relationship between said reflector surfaces andsaid diaphragm being such that lines perpendicular to the respectivesides of said diaphragm and forming equal angles of incidence andreflection with a corresponding one of said surfaces are directedthrough said opening.

GEORGE F. DEVINE.

REFERENCES CITED UNITED STATES PATENTS Name Date Brown Oct. 27, 1936Number

